I agree with Marionette, you already have the best on-site deal. Here are some money saving tips that I've used in the past to help with costs once I'm there:
Use one of the on-line shopping places (Garden Grocer) is one to order snacks, water, breakfast for the room. My family does't eat a big breakfast so we'll have a breakfast bar, piece of fruit, etc. I pack a small collapsible cooler which I keep in the bathtub and ziplock bags for ice. I get milk and yogurt which we keep in the cooler. I bring a small bag with water and some snacks into the park with us. With the ages of your children I'm assuming you'll have a stroller so its easy to carry with you.
I stock up on Disney items at home from the Dollar Store, Target,
Disney store clearance, etc. and bring them with me. Each night Tinkerbelle leaves a small gift. This helps to cut out on the souvenirs.
I get a lanyard and some trading pins for each child on ebay so they can trade pins. Much less expensive than in the parks.
Each child has a set dollar amount for souvenirs.
As we exit through the gift shops during the week we take pictures of what they think they want. On the last day we shop.Many counter meals can be shared - they really give you quite a bit of food.
Have a great time!